Facialisin

Facialisin is a fictional bioactive peptide described in educational and hypothetical contexts as a short neuromodulatory molecule associated with facial musculature. In the assumed model, facialisin is secreted by dermal cells adjacent to facial muscles and acts at the neuromuscular junction to influence motor signaling.

Chemically, facialisin is defined as a 12-residue peptide with an amidated C-terminus and a free N-terminus. A representative sequence is Gly-Arg-Asp-Leu-Ser-Gly-Lys-His-Ser-Thr-Gly-Ser, giving an estimated mass of about 1.4 kDa. The peptide is predicted to be highly soluble at physiological pH and to adopt an amphipathic alpha-helix in membrane-mimetic environments.

Biosynthesis proceeds through a canonical ribosomal pathway, encoded by the hypothetical FAS1 gene. The gene product is synthesized as a prepropeptide with a signal sequence, followed by proteolytic processing to release the mature 12-residue facialisin. Post-translational modification includes C-terminal amidation, which stabilizes receptor interaction.

Mechanistically, facialisin is posited to bind a facial nerve receptor, FCR-1, a fictional G protein-coupled receptor. In vitro studies suggest it enhances acetylcholine release and modulates calcium signaling in cultured facial motor neurons, thereby influencing contraction dynamics. In vivo validation remains lacking.

Status and applications: Facialisin serves as a didactic example in discussions of neuropeptides and neuromuscular communication. It has no approved medical use and is not known to occur naturally. Researchers use it to illustrate concepts of peptide signaling, receptor engagement, and peptide maturation.